1. Field of the Invention
The present invention relates to a scheduling technology, and it particularly relates to a method for allocating channels to terminal apparatuses to be communicated and a base station apparatus utilizing said method.
2. Description of the Related Art
In wireless communication, it is generally desired that the limited frequency resources be used effectively. With the wide use of mobile phones and second-generation cordless telephone system, such a demand is ever increasing. One of technologies that meet this request is a technique called OFDMA (Orthogonal Frequency Division Multiple Access). OFDMA is a technique where communications between a base station apparatus and a plurality of terminal apparatuses are performed at the same timing by allocating transmit signals from the terminal apparatuses to mutually orthogonal frequency bands. In general, the OFDMA technique requires scheduling processing for allocating a plurality of terminal apparatuses to the respective frequency bands. In the conventional practice, a frequency band whose SN ratio is high in a plurality of frequency bands is allocated to the terminal apparatuses.
In general, there are cases where in communications of high data rates a plurality of frequencies are allocated to one terminal apparatus. In such a case, a frequency band to be allocated to a terminal apparatus is selected based on an average value of SN ratios in a plurality of frequency bands. Here, there are cases where frequency bands whose SN ratios are low are contained due to the effect of frequency selective fading and the like even if the average value of SN ratios is high. In this case, retransmission may be frequently required. On the other hand, if channel allocation to such frequency bands is prohibited, a problem will arise where resources cannot be utilized effectively.